Air filtering material



- Enicst'O. Crocker, neimtntzana-miwaramniulngs, Acton,-Mass., asslgnors to Arthur-=1).

Little, Inc., a corporation of Massachusetts Serial No. 719,894

1 Ne Drawing. Application April- 10, 1934.

Our invention relates to filters 7 materials for use infiltering air and'other gases.

More particularly,it relates to materials or substances: of an oily nature to which dust or the like will adhere, such substance being applied to glass wool or othermaterial forming the base or supporting mediu'm therefor.

, therto, the so-called adhesive or dust catch-.

ling and retaining material used on filters has been it) typically a. petroleum oil, more or less thickened by the solution therein of soaps or similar sub- Such a material is effective as a dust stances.

catcher and retainer, but suffers from two serious defects: first, oil drains slowly away from the fibrous base during a considerable portion of the life of the filter, making for unsightliness and fire hazard; and second, if flame reaches an air.

filter, serious fire may result from the combustion of the oily adhesive finely dispersed over the fibrous base. f V

' Attempts to lessen this hazard have been made 12 Claims. (01. 183 -45) and filtering portions of the ingredients maybe varied to suit the particularrequirements of each case; we have found that, for example, 100 parts by weight each by use of very heavy oils, which are relatively less inflammable, though freely combustiblewhen ignited. This results in lowered dust-collecting efficiency, for such heavy oils, by virtue of their extreme viscosity, are poor adhesives. Other ate tempts have. been made to, securenon-i'nfiammability by the addition of highly-chlorinated organic compounds to oils of moderate viscosity. All of the. truly flame-proof chlorinated come pounds, such as -the chlorinated naphthalenes' -,and the chlorinated -diphenyls,-are themselves 1i 'so1ids,'and when usedin sufiicient amount to secure reasonable fire-proofness, render the oil a pasty solid which has very low dust-catching efficiency, and usually has decided. odor.

l object of our invention is to overcome the above noted drawbacks to dust catching materials heretofore in use, and to provide a non-inflam- 40. rna'ble, odorless and inexpensive'material to which dust will readily adhere and having a large capacity-for holding-dust and which, moreover, is

' adapted-to-be' appliedto glass wool or other w J fibrous-materials used for air' filters.

' which is-available commercially as Lindol, is a material having'thedesirableproperties hereinbefore set'forth and adapted to the purposes. of

" our invention. Tricresyl phosphate, although of 5o relatively low ,ViSCOSltY, can, by the method of this invention, be caused to adhere firmly to the We have discovered that tricresyl phosphate,

' glass wool-or other base of the filter. In -carry ingio'ut this invention, we first prepare an aqueous of tricresyl, phosphate and water, together with about 2 parts of'soap, make asatisfactory emulsion. After applying the emulsion, by any desired means, to the glass wool or other base, the water contained in the emulsion is driven off.

This results in the firm attachment of the tricresyl phosphate to the fibres of the base, by

. means of the soap or other emulsifying agent.

I If tricresyl phosphate isused alone on glass wool or similar base, it does not adhere closely, and drains off more or less in the course of time,

thereby damaging the product as regardslbotheffectiveness and. appearance. When applied in the manner of this invention, however, the tricresyl phosphate is dispersed in and on'the emule sifying agent, and is well attached so that the tendency to drain away'over a period of time is largely eliminated. The emulsifier should have thiscapacity to disperse and to hold the dustcatching medium, and shouldalso' be capable of coating or wetting the fibres of glass or other material instead of collecting along their length in a series .of spaced droplets characteristic of materials which do not .wet the glass.

The non-inflammable properties of the adhesive material are-apparently due to its breakdown, when exposed to flame, whereby smoke or gases consisting largely of fully oxidized (and hence not further combustible) "materials are produced. In the case of tricresyl phosphate (Lindol), this oxidized material is rich in P205 which apparently acts to blanket the flame and prevent it from spreading further.

In cases where flame-proof characteristics are of little importance, thin petroleum oils may be usedin the same way and with practically the same effectiveness as tricresyl phosphate." -Similarly, mixtures of thelatter with such oils may be used, where some flame-resistance is desired.

We claim:

1 A filtering Imaterial comprising a fibrous base, and a coating of tricresyl phosphate.

2. A filtering material comprising; a fibrous .bas e, anda coating of tricresyl phosphate finely dispersed and firmly anchored to said base.

' 3. A filtering materialcomprising glass wool, and a coating of tricresyl phosphate anchored thereto.

4. The. method which comprises emulsifying tricresyl phosphate with a water-soluble agent, emulsion of the'tricres'yl phosphate, using a suit- I able emulsifiersuch as common soda soap. Pro

applying the emulsion to a base of fibrous material, and driving off the water contained in the v as a coating to said fibrous base.

5'. The method 01'. forming a filtering material which comprises emulsifying tricreayl phosphate with a soda soap, applying the. emulsion to a base of fibrous material, and driving oil the water from said emulsion, leaving the tricres'yl phosphate as a coating adhering to said fibrous material.- 5

6. A filtering material comprising a base or glass wool, and a coating thereon of oily material comprising tricresyl phosphate finely die persed and adhering to the wool. I I

7. "A filtering material comprising anbrous baae;

and a coating thereon or an ester oi. an' acid oi phosphorus,

. graze emulsion, leaving the tricresyl phosphate adhering- 8. A filtering material comprising a fibrous base, and a coating thereon compriainga' mixture or petroleum oil and tricresyl phosphate. n i 9. Aillter comprising a base. and a coating 1. thereon 01' an ester oi an acidlot phosphorus.

10. A nlter comprising a base, and a coating thereon of tricresylphosphate. 1

' 1 1. A gas filtering material-comprising a porous I fibrous base, and a coating thereon or tricreayl phosphate. Y

a 12. A gas filter comprising-a porous base: anda coating thereon oftrlcresyi phosphate.

ERNEST C.'CROCKER. nowann J.BH.L1N GS. 

